When fitting an intraluminal endoprosthesis in place, the operator depends entirely on medical imaging. The small dimensions of the endoprostheses and the low contrast of the images mean that it is very difficult, even for an experienced operator, to guarantee 100% correct positioning. This is particularly true of self-expanding endoprostheses, which have a tendency to deploy completely when they emerge from the applicator and which it is difficult, if not impossible, to reposition.
Numerous applicators are known that are supposed to permit retraction and subsequent repositioning.
U.S. Pat. No. 5,026,377 discloses an applicator for a self-expanding stent. The proximal end of the stent is fixed to a central pusher by an adhesive or by the presence of a bead placed on this pusher. U.S. Pat. No. 5,628,755 and U.S. Pat. No. 5,246,421 describe applicators for plastically deformable stents (balloon stents). In U.S. Pat. No. 5,628,755, a sheath allows the length of the balloon to be adapted to stents of different lengths.
WO 96/13228 discloses an applicator equipped with a malleable core placed on the pusher for holding an endoprosthesis in place until it has been completely released.
WO 99/47075 describes a reversible applicator for an endoprosthesis, comprising an internal balloon that ensures that the applicator engages on the endoprosthesis until it has completely emerged from its housing.
In practice, none of these applicators gives 100% reliable results: once quite a limited length of the stent has been released, it is impossible to reverse it in order to correct its position. All these devices are also quite bulky because of the presence of the retention device inside the sheath, which fact automatically places a limit on the diameter of the vessels in which they can be employed.
EP-829 242 describes a catheter for removing an expanding endoprosthesis already implanted in a duct. The transport catheter comprises and outer tube and an axially moving inner tube. The inner tube bears hooks at its free end. When it is pushed outwardly, the hooks extend out of the catheter tube and spread, gripping the prosthesis so that it can theoretically be compressed and pulled into the catheter.
US 2004/0181237 relates to medical devices for manipulating medical implants such as, for example, stents, distal protection filters, and septal occluders in a patient's body, and the methods of use thereof. This medical device includes a sleeve and an expandable component joined to the sleeve which transitions between a collapsed configuration and a deployed configuration for capturing a medical implant in a patient's body.
In fact, it has proven practically impossible to remove a luminal endoprosthesis once it has been left in close contact with the wall of a vessel.
It has thus been sought to develop an applicator which takes up minimal space, that is to say occupies a small diameter when folded up, and which permits reversal of the positioning of an endoprosthesis until an advanced stage of the deployment procedure.